709 research outputs found
Disc atmospheres and winds in X-ray binaries
We review the current status of studies of disc atmospheres and winds in low
mass X-ray binaries. We discuss the possible wind launching mechanisms and
compare the predictions of the models with the existent observations. We
conclude that a combination of thermal and radiative pressure (the latter being
relevant at high luminosities) can explain the current observations of
atmospheres and winds in both neutron star and black hole binaries. Moreover,
these winds and atmospheres could contribute significantly to the broad iron
emission line observed in these systems.Comment: Accepted for publication in Acta Polytechnica. Invited review talk at
the Vulcano Workshop 2012: "Frontier Objects in Astrophysics and Particle
Physics
MAXI J1659-152: the shortest orbital period black-hole binary
Following the detection of a bright new X-ray source, MAXI J1659-152, a
series of observations was triggered with almost all currently flying
high-energy missions. We report here on XMM-Newton, INTEGRAL and RXTE
observations during the early phase of the X-ray outburst of this transient
black-hole candidate. We confirm the dipping nature in the X-ray light curves.
We find that the dips recur on a period of 2.4139+/-0.0005 hrs, and interpret
this as the orbital period of the system. It is thus the shortest period
black-hole X-ray binary known to date. Using the various observables, we derive
the properties of the source. The inclination of the accretion disk with
respect to the line of sight is estimated to be 60-75 degrees. The companion
star to the black hole is possibly a M5 dwarf star, with a mass and radius of
about 0.15 M_sun and 0.23 R_sun, respectively. The system is rather compact
(orbital separation is about 1.35 R_sun) and is located at a distance of
roughly 7 kpc. In quiescence, MAXI J1659-152 is expected to be optically faint,
about 28 mag in the V-band.Comment: 5 pages, 4 figures, to be published in the proceedings of the 4th
International MAXI Workshop `The First Year of MAXI: Monitoring variable
X-ray sources', 2010 Nov 30 - Dec 2, Tokyo, Japa
Stellar-Mass Black Holes and Their Progenitors
If a black hole has a low spin value, it must double its mass to reach a high
spin parameter. Although this is easily accomplished through mergers or
accretion in the case of supermassive black holes in galactic centers, it is
impossible for stellar-mass black holes in X-ray binaries. Thus, the spin
distribution of stellar-mass black holes is almost pristine, largely reflective
of the angular momentum imparted at the time of their creation. This fact can
help provide insights on two fundamental questions: What is the nature of the
central engine in supernovae and gamma-ray bursts? and What was the spin
distribution of the first black holes in the universe?Comment: Astro 2010 Science White Pape
ESO-Athena Synergy White Paper
The Advanced Telescope for High ENergy Astrophysics (Athena) is the X-ray
observatory mission selected by ESA within its Cosmic Vision 2015-2025
programme to address the Hot and Energetic Universe scientific theme. The
ESO-Athena Synergy Team (EAST) has been tasked to single out the potential
scientific synergies between Athena and optical/near-infrared (NIR) and sub/mm
ground based facilities, in particular those of ESO (i.e., the VLT and ELT,
ALMA and APEX), by producing a White Paper to identify and develop the: 1.
needs to access ESO ground-based facilities to achieve the formulated Athena
science objectives; 2. needs to access Athena to achieve the formulated science
objectives of ESO facilities contemporary to Athena; 3. science areas where the
synergetic use of Athena and ESO facilities in the late 2020s will result in
scientific added value. Community input to the process happened primarily via a
dedicated ESO - Athena Synergy Workshop that took place on Sept. 14 - 16, 2016
at ESO, Garching. This White Paper presents the results of the EAST's work,
sorted by synergy area, and deals with the following topics: 1. the Hot
Universe: Early groups and clusters and their evolution, Physics of the
Intracluster medium, Missing baryons in cosmic filaments; 2. the Energetic
Universe: Supermassive black hole (SMBH) history, SMBH accretion disks, Active
Galactic Nuclei feedback - Molecular outflows, Ultra-fast outflows, Accretion
Physics, Transient Science; 3. Observatory Science: Star Formation, Stars. It
then discusses the optical-NIR-sub-mm perspective by providing details on
VLT/MOONS, the E-ELT instruments, in particular the MOS, VISTA/4MOST, the ESO
and ALMA archives, future ALMA and ESO developments, and finally the (likely)
ESO - Athena astronomical scene in the 2020s. (abridged)Comment: 70 pages, 16 figure
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